Fretful words to a hospital receptionist (9)
I believe the answer is:
impatient
'fretful' is the definition.
(thesaurus)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for impatient that I've seen before include "Restless or short-tempered" , "Fidgety" , "Over-eager" , "Irritable" , "restive" .)